Mobile App Localization: The Complete 2024 Guide

Why Mobile Localization Matters

Mobile Localization Fundamentals

iOS Localization

iOS uses .strings files and .stringsdict for plurals:

// Localizable.strings (English)
"welcome_title" = "Welcome to Our App";
"items_count" = "%d items";
"settings_button" = "Settings";

// Usage in Swift
let title = NSLocalizedString("welcome_title", comment: "Welcome screen title")
// Or with SwiftUI
Text("welcome_title")

File Structure:

/YourApp
  /en.lproj
    Localizable.strings
    InfoPlist.strings
  /es.lproj
    Localizable.strings
    InfoPlist.strings
  /ja.lproj
    Localizable.strings
    InfoPlist.strings

Android Localization

Android uses XML resource files:

<!-- res/values/strings.xml (English) -->
<resources>
    <string name="welcome_title">Welcome to Our App</string>
    <string name="items_count">%d items</string>
    <string name="settings_button">Settings</string>
</resources>

<!-- res/values-es/strings.xml (Spanish) -->
<resources>
    <string name="welcome_title">Bienvenido a Nuestra App</string>
    <string name="items_count">%d elementos</string>
    <string name="settings_button">Configuración</string>
</resources>

// Usage in Kotlin
val title = getString(R.string.welcome_title)

React Native Localization

Common approach with react-i18next:

// i18n.js
import i18n from 'i18next';
import { initReactI18next } from 'react-i18next';

i18n.use(initReactI18next).init({
  resources: {
    en: { translation: require('./locales/en.json') },
    es: { translation: require('./locales/es.json') },
  },
  lng: 'en',
  fallbackLng: 'en',
});

// Component usage
import { useTranslation } from 'react-i18next';

function WelcomeScreen() {
  const { t } = useTranslation();
  return <Text>{t('welcome_title')}</Text>;
}

The App Store Problem

Traditional mobile localization has a major issue: updating translations requires a new app release.

The painful process:

What can go wrong:

OTA Translation Updates: The Solution

Over-the-Air (OTA) updates let you push translation changes directly to users without app store releases.

How It Works

IntlPull OTA Implementation

iOS (Swift):

import IntlPull

// Initialize at app launch
IntlPull.configure(
    projectId: "your-project-id",
    apiKey: "your-api-key"
)

// Use translations
let title = IntlPull.t("welcome_title")

// Translations update automatically in background

Android (Kotlin):

import com.intlpull.sdk.IntlPull

// Initialize in Application class
IntlPull.configure(
    projectId = "your-project-id",
    apiKey = "your-api-key"
)

// Use translations
val title = IntlPull.t("welcome_title")

React Native:

import IntlPull from '@intlpull/react-native';

// Initialize
IntlPull.configure({
  projectId: 'your-project-id',
  apiKey: 'your-api-key',
});

// Use hook
function WelcomeScreen() {
  const { t } = useIntlPull();
  return <Text>{t('welcome_title')}</Text>;
}

Benefits of OTA Updates

Localization Best Practices

1. Design for Localization

Allow for text expansion:

// Bad
label.frame = CGRect(x: 0, y: 0, width: 100, height: 20)

// Good
label.sizeToFit()
// or use Auto Layout constraints

2. Handle Pluralization

English has 2 plural forms. Arabic has 6. Russian has 3.

iOS (stringsdict):

<dict>
    <key>items_count</key>
    <dict>
        <key>NSStringLocalizedFormatKey</key>
        <string>%#@items@</string>
        <key>items</key>
        <dict>
            <key>NSStringFormatSpecTypeKey</key>
            <string>NSStringPluralRuleType</string>
            <key>one</key>
            <string>%d item</string>
            <key>other</key>
            <string>%d items</string>
        </dict>
    </dict>
</dict>

Android:

<plurals name="items_count">
    <item quantity="one">%d item</item>
    <item quantity="other">%d items</item>
</plurals>

3. Format Numbers, Dates, Currencies

// iOS
let formatter = NumberFormatter()
formatter.numberStyle = .currency
formatter.locale = Locale.current
let price = formatter.string(from: 99.99)
// US: "$99.99", Germany: "99,99 €", Japan: "¥100"

// Android
val format = NumberFormat.getCurrencyInstance(Locale.getDefault())
val price = format.format(99.99)

4. Handle RTL Languages

Arabic, Hebrew, and Persian read right-to-left.

// iOS - mostly automatic, but check:
view.semanticContentAttribute = .forceRightToLeft

<!-- Android - enable RTL support -->
<application android:supportsRtl="true">

5. Localize Images and Media

Some images contain text or culturally-specific content:

// iOS
let imageName = NSLocalizedString("hero_image", comment: "")
imageView.image = UIImage(named: imageName)

6. Test with Pseudolocalization

Before real translations, test with pseudo-translations:

"Welcome" → "[Ẃéĺćőḿé !!!]"

This helps find:

Translation Workflow

1. Extract Strings

Manual:

With IntlPull CLI:

# Automatically find and extract strings
npx intlpull scan --platform ios
npx intlpull scan --platform android

2. Manage Translations

Without a TMS:

With IntlPull:

3. Deploy Translations

Traditional:

# Build new app version
xcodebuild archive...
# Submit to App Store
# Wait...

With OTA:

# Just push to IntlPull
npx intlpull push

# Or click "Publish" in dashboard
# Users get updates immediately

Common Mistakes

1. Concatenating Strings

// Bad - word order varies by language
let message = "Hello " + name + ", welcome!"

// Good
let message = String(format: NSLocalizedString("greeting", comment: ""), name)
// "greeting" = "Hello %@, welcome!"

2. Assuming Text Length

// Bad
button.setTitle("OK", for: .normal)
button.frame.size.width = 40 // Breaks in German: "Einverstanden"

// Good
button.sizeToFit()
// or use >= constraints

3. Hardcoding Date Formats

// Bad - US format won't work everywhere
let dateString = "12/31/2024"

// Good
let formatter = DateFormatter()
formatter.dateStyle = .medium
formatter.locale = Locale.current

4. Forgetting App Store Metadata

Don't forget to localize:

Tools Comparison

Getting Started

Step 1: Audit Current State

Step 2: Choose Your Tools

For most mobile teams, IntlPull offers the best combination:

Step 3: Set Up

# Install CLI
npm install -g @intlpull/cli

# Initialize project
intlpull init

# Scan for strings
intlpull scan --platform ios
intlpull scan --platform android

# Add OTA SDK to your app
# iOS: pod 'IntlPull'
# Android: implementation 'com.intlpull:sdk:1.0.0'

Step 4: Integrate OTA

Follow platform-specific guides in our documentation.

Conclusion

Mobile localization doesn't have to be painful. With the right approach:

Ready to simplify mobile localization? Start free with IntlPull and ship translations without app store delays.